c#解决堂弟的某次笔试题

场景描述：

武汉热浪网吧收费标准如下：

6：00-12：00收费5.5/h，实时收费

12：00-18：00收费6/h，实时收费

18：00-23：00收费7/h，实时收费

23：00-第二天6：00，收费5/h，上限15收费

上限收费指实时收费超出上限时，按照上限收费，否则实时收费。

一.声明时段对象：

    /// <summary>
    /// 时段收费区间
    /// </summary>
    public class State
    {
        public TimeSpan start { get; set; }
        public TimeSpan end { get; set; }
        public double pay { get; set; }
        public double maxpay { get; set; }

        /// <summary>
        /// 某时间内的费用/小时
        /// </summary>
        /// <param name="_start">开始时间</param>
        /// <param name="_end">结束时间</param>
        /// <param name="_pay">每小时费用</param>
        /// <param name="_maxpay">时段上限收费，为0时代表实时收费</param>
        public State(TimeSpan _start, TimeSpan _end,double _pay,double _maxpay)
        {
            this.start = _start;
            this.end= _end;
            this.pay = _pay;
            this.maxpay = _maxpay;
        }
    }

二.计算类

    public class Compute
    {
        List<State> states = null;
        public Compute(List<State> _states)
        {
            this.states = _states;
        }

        public double GetResult(DateTime start,DateTime end)
        {
            double result = 0;
            if (this.states != null)
            {
                TimeSpan totlaSpan = end - start;
                if (totlaSpan.TotalDays >= 1)
                {
                    int days = Convert.ToInt32(totlaSpan.TotalDays);
                    result += FullDayPay() * days;
                    //证明有余的天数
                    if ((totlaSpan.TotalDays - days) > 0)
                    {
                        this.TimespanPay(start.AddDays(days), end, ref result);
                    }
                }
                else
                {
                    this.TimespanPay(start, end, ref result);
                }
            }
            return result;
        }

        /// <summary>
        /// 按时段收费
        /// </summary>
        /// <param name="start"></param>
        /// <param name="end"></param>
        /// <returns></returns>
        private void TimespanPay(DateTime start,DateTime end,ref double result)
        {
            // 时间所处的时段收费区间
            State spanState = this.GetSpan(start);
            // 此收费区间段结束时间
            DateTime spanEnd = new DateTime(start.Year, start.Month, start.Day).Add(spanState.end);
            TimeSpan span;
            bool next = false;
            // 如果结束时间在收费区间段之内
            if (end < spanEnd)
            {
                //计算结费总的时长
                span = end - start;
            }
            else
            {
                span = spanEnd - start;
                next = true;
            }
            // 计算区间内费用
            double payment = span.TotalHours * spanState.pay;
            if (spanState.maxpay > 0)
            {
                result += Math.Min(payment, spanState.maxpay);
            }
            else
            {
                result += payment;
            }
            if (next)
            {
                this.TimespanPay(spanEnd, end, ref result);
            }
        }

        /// <summary>
        /// 根据开始时间获取所属的时段
        /// </summary>
        /// <param name="start"></param>
        /// <returns></returns>
        private State GetSpan(DateTime start)
        {
            IEnumerable<State> states = this.states.Where(a => start >= new DateTime(start.Year, start.Month, start.Day).Add(a.start));
            return states.Last();
        }

        /// <summary>
        /// 获取全天的收费
        /// </summary>
        /// <returns></returns>
        private double FullDayPay()
        {
            double result = 0;
            foreach (State item in this.states)
            {
                if (item.maxpay > 0)
                {
                    result += item.maxpay;
                }
                else
                {
                    result += (item.end - item.start).TotalHours * item.pay;
                }
            }
            return result;
        }
    }

三.调用

           List<State> states = new List<State>
            {
                new State(new TimeSpan(6,0,0),new TimeSpan(12,0,0),5.5,0),
                new State(new TimeSpan(12,0,0),new TimeSpan(18,0,0),6,0),
                new State(new TimeSpan(18,0,0),new TimeSpan(23,0,0),7,0),
                new State(new TimeSpan(23,0,0),new TimeSpan(1,6,0,0),5,15),
            };

            //假如上网时间从2019-9-20 17：23-2019-9-22 22：10
            DateTime start = new DateTime(2019,9,20,17,23,0);
            DateTime end = new DateTime(2019, 9, 22, 22, 10, 0);

            Compute c = new Compute(states);
            Console.WriteLine(c.GetResult(start, end));